1. Field of the Invention
The present invention relates generally to the preparation of substrates such as those used in semiconductor fabrication as well as in the manufacture of hard disk drives, and more particularly to the cleaning and drying of substrates using space- and process-efficient systems.
2. Description of the Related Art
In the fabrication of semiconductor devices, there is a need to perform a variety of substrate preparation operations including chemical mechanical polishing (CMP) operations and substrate cleaning. By way of example, integrated circuit devices are commonly fabricated as multi-level structures. Planarization, polishing, and cleaning operations are typically performed on semiconductor wafers at various stages in the fabrication process to maintain a smooth and constant topography, as well as to remove excess metallization during the process of forming metal line patterns throughout the wafer. In the fabrication of hard disk drives, planarization and cleaning operations are needed to maintain a clean and smooth disk substrate.
Typical substrate cleaning, polishing and planarization techniques can include the independent processes of immersion and preparation of a substrate using a megasonic apparatus, followed by scrubbing, buffing, polishing, or other such operations using a scrubbing or polishing apparatus, and a rinse and dry operation using a spin, rinse and dry (SRD) apparatus. Such processes are often repeated a plurality of times, interspersed at various stages of substrate preparation and fabrication.
In the prior art, substrate cleaning systems typically implement brush stations in which polyvinyl alcohol (PVA) brushes are used to scrub both sides of a substrate. The PVA brush material is configured to be soft enough to prevent damage to the substrate""s delicate surface, yet can provide good mechanical contact with the substrate surface to dislodge residues, chemicals and particulates. In some applications, the process is enhanced by performing a megasonic preparation process on a substrate prior to processing the substrate through such a cleaning system. In the megasonic processing, a cassette of substrates is typically immersed in a tank and subjected to megasonic energy to loosen, soften, dislodge, or otherwise enhance the removal of residues, chemicals and particulates in the cleaning system. Following a megasonic processing, a cassette of substrates is then commonly transported to a cleaning system for continued substrate preparation.
Each of the brushes in a cleaning system are typically configured to deliver chemicals and or DI water through the brush (TTB). Two brush stations are often used, each with a pair of brushes, to enable the application of chemicals in one brush station and DI water in the other. This dual brush station approach has been shown to improve the cleaning performance as well as increase throughput. One physical layout of the cleaning system is to arrange the brush stations longitudinally (i.e., horizontally). The substrate therefore travels from one brush station to the next along a conveying system.
Once the substrate has been processed in both brush stations, the substrate is then transported to a next station in which the substrate is subjected to an SRD operation, which is performed in an SRD station or dryer station.
Each of the megasonic processing, scrubbing, polishing, buffing, or cleaning processing, and SRD processing is typically accomplished by separate apparatus or machines, and often arranged sequentially or in close proximity to perform sequential processing operations. Where these substrate processing stations are arranged horizontally, the machine or machines necessarily occupy a large clean room footprint. In some systems, a single machine footprint can be as long as 6-7 feet by 3 feet wide.
The footprint of a cleaning system is significantly reduced when the preparation systems are arranged in a vertical orientation. The vertical arrangement results in reduced costs of manufacture by reducing the footprint of preparation systems and requiring less clean room floor space.
In some substrate fabrication operations, the combination of megasonic preparation with scrub, polish, buff, or clean operations, and followed by a SRD process is a most preferred process. Because of stringent cleanliness requirements, transfer between preparation stations must be minimized, and the preparation environment must meet exacting specifications. Further, economy of process and the demands of output necessitate batch processing of substrates whenever possible.
In view of the foregoing, there is a need for substrate preparation systems and methods that are more compact, occupy smaller clean room footprints, provide for more efficient and higher throughput substrate preparation operations (e.g., such as cleaning, etching, drying and the like), allow for multiple scrub, polish, buff, or clean operations and maintain stringent clean room specification requirements. These substrate preparation systems and methods should therefore be configured to avoid the problems of the prior art.
Broadly speaking, the present invention fills these needs by providing a system and method for substrate preparation that provides for batch preparation of substrates within a compact and efficiently designed system enclosure. The present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a substrate preparation system is disclosed. The substrate preparation system includes an immersion in a lower front of the system that is configured to receive a cassette of substrates for megasonic processing. The substrate preparation further includes a brush box unit in a lower back end of the system, and a dryer unit positioned over the brush box unit. A robot arm is positioned between the immersion tank and the brush box and dryer units, and is configured to transport substrates from the immersion tank to the brush box, and from the brush box to the dryer unit. The substrate preparation system is configured to contain the immersion tank, the brush box unit, the dryer unit and the robot arm within the substrate preparation system.
In another embodiment, a method for preparing a substrate is disclosed. The method includes providing a batch of substrates, and immersing the batch of substrates in an immersion tank. The method further includes the processing of the substrates following immersion to include transitioning of a substrate from the immersion tank to a first brushing station, transitioning the substrate from the first brushing station to a second brushing station, transitioning the substrate from the second brushing station to an drying station, and transitioning the substrate from the drying station to a clean output cassette. The method provides for continuous and successive substrate processing for a desired number of batches of cassettes.
In still a further embodiment, a wafer processing system is disclosed. The wafer processing system includes a system enclosure containing wafer processing apparatus within an isolated wafer processing environment. The wafer processing system further includes a pair of immersion tanks in the lower front of the system that are configured to process wafers in a fluid bath, a pair of wafer pickers to extract wafers from the fluid bath, a robot arm behind the immersion tanks that transitions wafers from the wafer pickers across the system enclosure, a pair of brush boxes in the lower back region of the system that scrub substrates received from the robot, a pair of dryer units above the brush boxes that receive wafers from the robot after the robot extracts the wafers from the brush boxes, and a pair of output shelves located in the upper front region of the system enclosure above the pair of immersion tanks, the output shelves supporting output cassettes which receive wafers from the robot after the wafers have been processed in the dryer units.
The advantages of the present invention are numerous. One notable benefit and advantage of the invention is that a plurality of substrate preparation operations can be accomplished within a single, compact, and efficient system. The system maintains an isolated, clean environment which minimizes substrate exposure to or risk of contamination while transitioning between the plurality of process operations. The efficient arrangement of the process apparatus allows for minimal transfer distance between process apparatus.
Another benefit is the incorporation of megasonic processing in one embodiment. After immersing substrates in a liquid bath being of some chemical or water composition in one or both immersion tanks, the substrates are then subjected to megasonic energy. This processing is configured to loosen, soften, dislodge, or otherwise enhance the removal of residues, chemicals and particulates from substrates in the subsequent scrubbing, cleaning, polishing, buffing, or other such process.
Another benefit is the substrate processing apparatus assembled within the system enclosure. The system provides for multiple batch processing of wafers resulting in increased throughput of substrates and decreased time required for substrate fabrication and preparation.
Yet another benefit is the efficient arrangement of the system apparatus. The disclosed system units can be assembled in modular combinations, and the illustrated embodiments of the vertically arranged dryer units over brush boxes, output shelves over immersion tanks, and transfer robot provide a self-contained class 1 clean room environment within a system enclosure that requires much less fab and clean room floor space than in the prior art. This both maximizes the cleanliness of the substrate processing environment, and reduces the cost of fabrication and processing by requiring less floor space.
Other advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.